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Updated: Jul 19, 2026

Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators
Published on: May 30, 2014
Generation of a superposition of odd photon number states for quantum information networks
J S Neergaard-Nielsen1, B Melholt Nielsen, C Hettich
1Niels Bohr Institute, Copenhagen University, DK 2100, Denmark and QUANTOP, Danish National Research Foundation Center for Quantum Optics, Denmark.
Abstract:
We report on the experimental observation of quantum-network-compatible light described by a nonpositive Wigner function. The state is generated by photon subtraction from a squeezed vacuum state produced by a continuous wave optical parametric amplifier. Ideally, the state is a coherent superposition of odd photon number states, closely resembling a superposition of weak coherent states |alpha > - |-alpha >. In the limit of low squeezing the state is basically a single photon state. Light is generated with about 10,000 and more events per second in a nearly perfect spatial mode with a Fourier-limited frequency bandwidth which matches well atomic quantum memory requirements. The generated state of light is an excellent input state for testing quantum memories, quantum repeaters, and linear optics quantum computers.
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